Jonathan Edwards writes in Freedom of the Will about moral ability and natural ability.

We are said to be naturally unable to do a thing, when we cannot do it if we will, because what is most commonly called nature does not allow of it, or because of some impeding defect or obstacle that is extrinsic to the Will; either in the Faculty of understanding, constitution of body, or external objects. Moral Inability consists not in any of these things; but either in the want of inclination; or the strength of a contrary inclination; or the want of sufficient motives in view, to induce and excite the act of the Will, or the strength of apparent motives to the contrary.

There is absolutely no way that I would ever leave my daughter on the side of the road and drive off.  Even if I wanted to be free from the responsibility, cost, and stress of raising her, it would be impossible for me to abandon her like that.  It is impossible, not because I lack the physical capacity to do so, or the mental capacity to carry out such an operation.  There is no armed guard standing watch over her, preventing me from carrying out such a thing.  There is no innate human characteristic that precludes me doing this; other people have done such things.  No, it is impossible because I lack any inclination or motive to do such a thing; or even if such an inclination or motive were to make its existence known, it would immediately, without any question, be entirely overpowered by my strong desire to keep her, protect her, and love her.

In the same way, fallen humans are morally incapable of submitting their life to God.  Adam’s sin was to put himself in the place of God; evaluating for himself what is good and what is evil.  Every human ever since has done the same thing.  Fallen man has no inclination whatsoever for giving up his assumed role of arbiter of right and wrong.  He retains control of his human faculties of thought, emotion, speech and action, and can direct these faculties according to his will.  He retains the ability to decide who he will obey, and he retains the ability to act in accordance with his decision.  But his dead spirit leaves him no motivation to exercise his will in submission to God; or even if he thought that submission to God might be a good idea, his desire for autonomy would immediately overrule such a notion.  His human nature retains the freedom to choose in accordance with his will.  However, his will is corrupt and lacks the moral freedom to choose God.